Theoretical and experimental study of the solar transmittance of multiribbed materials

To estimate energy benefits, peak loads, efficiencies, and different potential risks such as overheating, thermal damage, or glare in buildings, knowledee of the behaviour of the envelope materials is required. An experimental tool, the Megasphere, for characterising the optical properties in the solar and visible range of semitransparent materials with macroscopic heterogeneity is presented. The whole experimental setup, and an application to solar transmittance of one type of material (multiribbed material), are presented. A theoretical model has been developed to predict the spectral transmittance of these types of materials. This model evaluates the global transmittance as a function of the angle of incidence with structural and dense material properties. The comparison between the experimental and the modelling approaches is presented and discussed, with representative results.